[PATCH net v2] net: airoha: Add dma_rmb() and READ_ONCE() in airoha_qdma_rx_process()

[Lorenzo Bianconi]

Add missing dma_rmb() in airoha_qdma_rx_process routine to make sure the
DMA read operations are completed when the NIC reports the processing on
the current descriptor is done. Moreover, add missing READ_ONCE() in
airoha_qdma_rx_process() for DMA descriptor control fields in order to
avoid any compiler reordering.

Fixes: 23020f0493270 ("net: airoha: Introduce ethernet support for EN7581 SoC")
Signed-off-by: Lorenzo Bianconi <lorenzo at kernel.org>
---
Changes in v2:
- Use msg1 in airoha_qdma_get_gdm_port() signature to avoid missing
  READ_ONCE().
- Link to v1: https://lore.kernel.org/r/20260402-airoha_qdma_rx_process-fix-reordering-v1-1-53278474f062@kernel.org
---
 drivers/net/ethernet/airoha/airoha_eth.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
index 95ba99b89428..f1843bc5b991 100644
--- a/drivers/net/ethernet/airoha/airoha_eth.c
+++ b/drivers/net/ethernet/airoha/airoha_eth.c
@@ -581,10 +581,9 @@ static int airoha_qdma_fill_rx_queue(struct airoha_queue *q)
 	return nframes;
 }
 
-static int airoha_qdma_get_gdm_port(struct airoha_eth *eth,
-				    struct airoha_qdma_desc *desc)
+static int airoha_qdma_get_gdm_port(struct airoha_eth *eth, u32 msg1)
 {
-	u32 port, sport, msg1 = le32_to_cpu(desc->msg1);
+	u32 port, sport;
 
 	sport = FIELD_GET(QDMA_ETH_RXMSG_SPORT_MASK, msg1);
 	switch (sport) {
@@ -612,15 +611,17 @@ static int airoha_qdma_rx_process(struct airoha_queue *q, int budget)
 	while (done < budget) {
 		struct airoha_queue_entry *e = &q->entry[q->tail];
 		struct airoha_qdma_desc *desc = &q->desc[q->tail];
-		u32 hash, reason, msg1 = le32_to_cpu(desc->msg1);
-		struct page *page = virt_to_head_page(e->buf);
-		u32 desc_ctrl = le32_to_cpu(desc->ctrl);
+		u32 hash, reason, msg1, desc_ctrl;
 		struct airoha_gdm_port *port;
 		int data_len, len, p;
+		struct page *page;
 
+		desc_ctrl = le32_to_cpu(READ_ONCE(desc->ctrl));
 		if (!(desc_ctrl & QDMA_DESC_DONE_MASK))
 			break;
 
+		dma_rmb();
+
 		q->tail = (q->tail + 1) % q->ndesc;
 		q->queued--;
 
@@ -633,10 +634,12 @@ static int airoha_qdma_rx_process(struct airoha_queue *q, int budget)
 		if (!len || data_len < len)
 			goto free_frag;
 
-		p = airoha_qdma_get_gdm_port(eth, desc);
+		msg1 = le32_to_cpu(READ_ONCE(desc->msg1));
+		p = airoha_qdma_get_gdm_port(eth, msg1);
 		if (p < 0 || !eth->ports[p])
 			goto free_frag;
 
+		page = virt_to_head_page(e->buf);
 		port = eth->ports[p];
 		if (!q->skb) { /* first buffer */
 			q->skb = napi_build_skb(e->buf, q->buf_size);
@@ -670,8 +673,8 @@ static int airoha_qdma_rx_process(struct airoha_queue *q, int budget)
 			 * DMA descriptor. Report DSA tag to the DSA stack
 			 * via skb dst info.
 			 */
-			u32 sptag = FIELD_GET(QDMA_ETH_RXMSG_SPTAG,
-					      le32_to_cpu(desc->msg0));
+			u32 msg0 = le32_to_cpu(READ_ONCE(desc->msg0));
+			u32 sptag = FIELD_GET(QDMA_ETH_RXMSG_SPTAG, msg0);
 
 			if (sptag < ARRAY_SIZE(port->dsa_meta) &&
 			    port->dsa_meta[sptag])

---
base-commit: ec7067e661193403a7a00980bda8612db5954142
change-id: 20260402-airoha_qdma_rx_process-fix-reordering-722308255b65

Best regards,
-- 
Lorenzo Bianconi <lorenzo at kernel.org>